Aqueous extracts of many plant seeds, such as soya beans, sunflower, peanut, cotton-seed, safflower, and sesame, are rich in protein and can be used as replacement of animal or human milk in many applications. The artificial milk made from soya beans has long been recognized as an inexpensive and healthy alternative to dairy milk. However, it has not been popular outside the Orient due to the objectionable beany flavour it has when made using traditional Oriental method.
Several methods have been developed to get rid of the beany flavour. When the seed is broken to extract protein and oil, the reaction of water, oxygen, and oils catalysed by lipoxygenase enzyme results in the formation of certain volatiles having foul odour. Most methods recognise lipoxygenase enzyme as the culprit and attempt to deactivate it by heat treatment or pH control of the aqueous medium of seed disintegration. The heat treatment of the seeds in these methods is done prior to or during the seed disintegration. However, the lipoxygenase enzyme being a protein, its deactivation results in the denaturing of other proteins in the seed. The extracted solids in water are thus not well dissolved and result in chalky mouth-feel and low product yield. Expensive processing is therefore required to make the product palatable.
One recent method taught in U.S. Pat. No. 4,915,972, Apr. 10, 1990 (Gupta et al) entirely depends on reducing the free oxygen to a few parts per million level in the disintegrating environment for eliminating the development of off-flavour. The enzyme is not deactivated by heat treatment until well after the seed solids are extracted in the aqueous medium. As a result the product has no chalky mouth-feel and the product yield is high. The present invention uses this method and is directed to a device to automatically make aqueous extracts of high protein seeds. The steps of grinding seeds in the aqueous medium, cooking the seed slurry, and separating aqueous the extract from undissolved solids are all accomplished automatically in a single vessel.
U.S. Pat. No. 4,744,524 May 17, 1988 (Gupta) describes a grinder/cooker that does the airless grinding and cooking of soy beans in a single vessel. It uses a process of grinding soy beans in oxygen-free environment and produces slurry of ground soy beans. Soy milk is extracted separately from the slurry.